/**
 * This file tests the top-chunk optimization logic in splitChunk command.
 * Whenever a chunk is split, the shouldMigrate field should be set if the extreme chunk
 * has only a single document, where extreme chunk is defined as the chunk containing
 * either the upper or lower bound of the entire shard key space.
 */

var st = new ShardingTest({ shards: 1 });
st.stopBalancer();

var testDB = st.s.getDB('test');
testDB.adminCommand({ enableSharding: 'test' });

var callSplit = function(db, minKey, maxKey, splitPoints) {
    var res = st.s.adminCommand({getShardVersion: "test.user"});
    assert.commandWorked(res);
    var shardVersion = [res.version, res.versionEpoch];
    return db.runCommand({
        splitChunk: 'test.user',
        from: 'shard0000',
        min: minKey,
        max: maxKey,
        keyPattern: { x: 1 },
        splitKeys: splitPoints,
        shardVersion: shardVersion,
    });
};

var tests = [
//
// Lower extreme chunk tests.
//

// All chunks have 1 doc.
//
// Expected doc counts for new chunks:
// [ MinKey, -2 ): 1
// [ -2, -1 ): 1
// [ -1, 0): 1
//
function(db) {
    var res = callSplit(db, { x: MinKey }, { x: 0 }, [{ x: -2 }, { x: -1 }]);
    assert.commandWorked(res);
    assert.neq(res.shouldMigrate, null, tojson(res));
    assert(bsonWoCompare(res.shouldMigrate.min, { x: MinKey }) == 0, tojson(res.shouldMigrate.min));
    assert(bsonWoCompare(res.shouldMigrate.max, { x: -2 }) == 0, tojson(res.shouldMigrate.max));
},

// One chunk has single doc, extreme doesn't.
//
// Expected doc counts for new chunks:
// [ MinKey, -1 ): 2
// [ -1, 0): 1
//
function(db) {
    var res = callSplit(db, { x: MinKey }, { x: 0 }, [{ x: -1 }]);
    assert.commandWorked(res);
    assert.eq(res.shouldMigrate, null, tojson(res));
},

// Only extreme has single doc.
//
// Expected doc counts for new chunks:
// [ MinKey, -2 ): 1
// [ -2, 0): 2
//
function(db) {
    var res = callSplit(db, { x: MinKey }, { x: 0 }, [{ x: -2 }]);
    assert.commandWorked(res);
    assert.neq(res.shouldMigrate, null, tojson(res));
    assert(bsonWoCompare(res.shouldMigrate.min, { x: MinKey }) == 0, tojson(res.shouldMigrate.min));
    assert(bsonWoCompare(res.shouldMigrate.max, { x: -2 }) == 0, tojson(res.shouldMigrate.max));
},

//
// Upper extreme chunk tests.
//

// All chunks have 1 doc.
//
// Expected doc counts for new chunks:
// [ 0, 1 ): 1
// [ 1, 2 ): 1
// [ 2, MaxKey): 1
//
function(db) {
    var res = callSplit(db, { x: 0 }, { x: MaxKey }, [{ x: 1 }, { x: 2 }]);
    assert.commandWorked(res);
    assert.neq(res.shouldMigrate, null, tojson(res));
    assert(bsonWoCompare(res.shouldMigrate.min, { x: 2 }) == 0, tojson(res.shouldMigrate.min));
    assert(bsonWoCompare(res.shouldMigrate.max, { x: MaxKey }) == 0, tojson(res.shouldMigrate.max));
},

// One chunk has single doc, extreme doesn't.
//
// Expected doc counts for new chunks:
// [ 0, 1 ): 1
// [ 1, MaxKey): 2
//
function(db) {
    var res = callSplit(db, { x: 0 }, { x: MaxKey }, [{ x: 1 }]);
    assert.commandWorked(res);
    assert.eq(res.shouldMigrate, null, tojson(res));
},

// Only extreme has single doc.
//
// Expected doc counts for new chunks:
// [ 0, 2 ): 2
// [ 2, MaxKey): 1
//
function(db) {
    var res = callSplit(db, { x: 0 }, { x: MaxKey }, [{ x: 2 }]);
    assert.commandWorked(res);
    assert.neq(res.shouldMigrate, null, tojson(res));
    assert(bsonWoCompare(res.shouldMigrate.min, { x: 2 }) == 0, tojson(res.shouldMigrate.min));
    assert(bsonWoCompare(res.shouldMigrate.max, { x: MaxKey }) == 0, tojson(res.shouldMigrate.max));
},
];

tests.forEach(function(test) {
    // setup
    testDB.adminCommand({ shardCollection: 'test.user', key: { x: 1 }});
    testDB.adminCommand({ split: 'test.user', middle: { x: 0 }});

    for (var x = -3; x < 3; x++) {
        testDB.user.insert({ x: x });
    }

    // run test
    test(st.d0.getDB('admin'));

    // teardown
    testDB.user.drop();
});

st.stop();

